JPH04219964A - Integrated circuit - Google Patents

Abstract

PURPOSE:To prevent an insulation resistance from being lowered when a contaminant such as a conductive foreign body or the like adheres between terminal pins, to enhance the airtight property of parts to which said terminal pins are attached and to prevent moisture, said contaminant, a corrosive gas and the like from creeping. CONSTITUTION:A terminal pin 3 at an integrated circuit is provided with a terminal-pin fixation structure, as indicated by a symbol A, by which it is fixed and held at prescribed accuracy by a plastic mold 12. An airtight and hermetical sealing structure as indicated by a symbol B is constituted of a sealing material, containing a silicone component, which contains a silicone and which is provided with a close contact property and an elastic property. Consequently, a stress such as a thermal stress or the like is not caused due to the difference between the coefficient of thermal expansion of the plastic mold 12 and the coefficient of thermal expansion of the terminal pin 3, and the airtight and hermetical sealing structure which is good can be kept. Thanks to the water-repellant property of the silicone, a contaminant which floats in the air hardly adheres even when it falls.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic molded integrated circuit having terminal pins on a package, and more particularly to an integrated circuit whose reliability can be improved.

0002

[Prior Art] In recent years, ceramic packages with good hermetic sealing characteristics have been used for integrated circuits that require high reliability. BACKGROUND ART Plastic molded packages, which can be manufactured into various package types such as packages, have come into use due to improvements in reliability due to improvements in mold resin properties and improvements in integrated circuit wafer chip surface protection technology.

[0003] It is known that thermal stress occurs in plastic molded integrated circuits due to heat generated during soldering when the integrated circuit is mounted on a printed circuit board, and temperature rise during energization after mounting. . This thermal stress is due to the difference in coefficient of thermal expansion of the plastic and that of the terminal pin at the interface between the plastic mold and the terminal pin.

[0004] Furthermore, if such thermal stress becomes excessive, a gap may occur at the interface between the plastic mold and the terminal pin, and furthermore, package cracks may occur on the surface of the plastic mold. There are cases where this happens.

[0005] When a gap or a package crack occurs at the interface between the plastic mold and the terminal pin as described above, moisture in the air, contaminants, corrosive gas, etc. are released from the gap or package crack. enters the inside of the integrated circuit, causing problems such as corrosion and disconnection of the aluminum wiring inside the integrated circuit.

Furthermore, in addition to the corrosion inside the package,
Trouble may also occur on the surface of the package.

FIG. 8 shows a DIP (dual in-li
ne package) is a side view showing the adhesion of contaminants around the terminal pins of the integrated circuit.

In FIG. 8, contaminants 40 have adhered around a total of three terminal pins 3 fixedly held in the plastic mold 12 of the integrated circuit 1.

If the attached contaminant 40 is a conductive foreign substance or becomes a conductive foreign substance by dissolving in the attached moisture due to dew condensation, the contaminants 40 between these terminal pins 3 There is a problem that the insulation resistance decreases or a complete short circuit occurs.

MOS (metal oxide)
Some integrated circuits (semiconductors) have very high input impedance at their input terminals. In such integrated circuits, even if the insulation resistance of the terminal pins decreases even slightly, it can degrade the electrical characteristics of the integrated circuit and the electronic circuit in which the integrated circuit is used, leading to malfunction. There is a problem in that it causes

FIG. 9 shows a PGA (pin grid)
FIG. 3 is a bottom view showing the adhesion of contaminants between terminal pins in a packaged integrated circuit.

In FIG. 9, symbols 1, 3, 12, 4
0 is the same as the one with the same symbol in FIG. 8 described above.

Also in the PGA package integrated circuit shown in FIG. 9, contaminants 40 that have adhered between the terminal pins 3
This causes a problem similar to that of the DIP integrated circuit shown in FIG. 8 described above.

FIG. 10 is an explanatory diagram of a gap created at the interface between a plastic mold and a terminal pin in a DIP integrated circuit.

In FIG. 10, the coefficient of thermal expansion of the plastic mold 12 of the integrated circuit 1 and the coefficient of thermal expansion of the terminal pin 3 are different.

Therefore, due to the temperature rise during soldering when this integrated circuit 1 is mounted on a printed circuit board, and the temperature rise due to energization after mounting, the integrated circuit 1 may become unstable as shown by reference numeral D in FIG. This creates gaps that impede airtightness.

If such a gap is created, contaminants and corrosive gas components in the air and the mold that have been dissolved or mixed in with the moisture that has condensed and adhered will enter the integrated circuit, causing the aluminum inside the integrated circuit to deteriorate. This may cause problems such as corrosion of wiring, etc.

Furthermore, contaminants 40 attached between the terminal pins 3
However, there are cases where dew condenses between the terminal pins 3 and dissolves in the attached moisture, causing a short circuit between the terminals.

FIG. 11 is an explanatory diagram of a gap that occurs at the interface between the plastic mold and the terminal pin of a PGA package integrated circuit.

In FIG. 11, symbols 1, 3, 12,
D is the same as the one with the same reference numeral in FIG. 10 described above.

In FIG. 11, the development process of the gap indicated by the symbol D is the same as that in FIG. 10 described above, and the trouble caused by this gap is also the same as in FIG.

FIG. 12 is a top view showing a corrosion breakage of aluminum wiring on a wafer chip inside an integrated circuit.

In FIG. 12, pads 30 connected to terminal pins provided on the integrated circuit package are arranged at the periphery of the wafer chip inside the integrated circuit.

This pad 30 is connected to an aluminum wiring 32
is connected to the input/output buffer section 34. or,
Further inside the wafer chip 5, predetermined wiring is provided using aluminum wiring 32.

The aluminum wiring 32 in the shaded areas indicated by symbols C1 and C2 in FIG. 12 is corroded.
The wire has been disconnected.

As mentioned above, if a gap is created at the interface between the plastic mold of the integrated circuit and the terminal pin, and airtightness is impaired, contaminants and corrosive gases in the air or in the mold can enter the inside of the integrated circuit. It will invade.

For example, if the invading contaminant is an alkali ion such as sodium or potassium, or a halogen ion such as chlorine, bromine, or the like, aluminum Wiring is corroded.

That is, the halogen ions move from the cathode side to the anode side, causing anode corrosion. or,
Alkaline ions move from the anode side to the cathode side,
The pH on the cathode side increases locally, requiring cathode corrosion.

For example, in the case of contamination where sodium ions and chloride ions coexist, the sodium ions migrate to the cathode side and a reaction as shown in the following equation proceeds.

a + +e − →Na Na +H2 O→Na + +OH− +H
......(1
)

When the pH on the cathode side increases due to the reaction of equation (1), a reaction as shown in the following equation occurs, and the aluminum wiring is corroded.

[0032] Al +3(OH)− →Al (OH)3 +3e
− O2 +2H2 O+4e − →4(OH)−
......(2
)

On the other hand, on the anode side, a reaction as shown in the following formula occurs, and a soluble salt is produced.

[0034] Al(OH)3 +Cl − →Al(OH)2
Cl +OH-……(3)

0035
] At the same time, the chlorine ions that are invading contaminants and the aluminum wiring undergo a reaction as shown in the following equation, and the aluminum wiring is corroded.

Al +4Cl − →(Al Cl 4) − +3e
- 2Al Cl 4 - +6H2 O→2Al
(OH)3 +6H+ +8Cl − …(4)

00
[37] Furthermore, as shown in equation (4), when the aluminum wiring is corroded, chlorine ions are simultaneously regenerated.

On the anode side, the above equations (3) and (4)
As shown in the equation, as the anodic oxidation of the aluminum wiring progresses, Al (OH)3 is produced, which reduces the rate of dissolution by chlorine ions.

Therefore, when aluminum wiring is corroded due to such contamination with sodium ions and chloride ions, the corrosion rate on the cathode side is faster than on the anode side.

[0040] As described above, when contaminants, moisture, or corrosive gas enter the inside of the integrated circuit, a problem arises in that the aluminum wiring inside the integrated circuit is corroded and disconnected.

Conventionally, in order to prevent corrosion of the aluminum wiring inside the integrated circuit, a passivation film such as a SiO2 film, a PSG film, or a Si nitride film has been formed on the surface of the wafer inside the integrated circuit. .

[0042] Furthermore, the following techniques have been disclosed regarding integrated circuits that can prevent gaps at the interface between the plastic mold of the integrated circuit and the terminal pins and package cracks.

[0043] This reduces the thermal expansion coefficient and improves the flexibility of the resin used for molding integrated circuits, thereby reducing the thermal stress (stress) that occurs when the temperature changes, and reducing the bending of the resin itself. It is a technology that improves strength, toughness, and adhesion, and 1M bite DR.
It is disclosed as a technology applied to AM (Nikkei Micro Devices, June 1990 issue, pages 58 to 62).

[0044]

[Problems to be Accomplished by the Invention] However, the above-mentioned passivation film for preventing corrosion of aluminum wiring on a wafer chip inside an integrated circuit, etc.
There is a problem in that resin sealing stress generated when an integrated circuit is sealed with a plastic resin causes damage to the passivation film. Therefore, it is a necessary condition to improve the hermeticity of the sealing of the integrated circuit itself.

[0045] Furthermore, as mentioned above, silicone-modified silicone resins are examples of adhesive resins that have a small coefficient of thermal expansion, are flexible, and have improved bending strength and toughness during sealing. There is a problem in that these resins are more expensive than commonly used epoxy resins.

[0046] Furthermore, the resin for the plastic mold of the integrated circuit must be capable of fixing and holding the terminal pins of the integrated circuit with a predetermined precision. For this reason, it is not preferable to improve the flexibility of the resin for plastic molds more than necessary. Therefore, given the limited flexibility of the resin, it is difficult to dramatically improve the reduction in thermal stress caused by temperature changes.

The present invention has been made to solve the above-mentioned conventional problems, and in a plastic molded integrated circuit having terminal pins on a package, there is a possibility that contaminants such as conductive foreign matter may adhere between the terminal pins. Provides an integrated circuit that can improve reliability by preventing a decrease in insulation resistance and improving the airtightness of the terminal pin mounting area to prevent moisture, contaminants, corrosive gas, etc. from entering. The purpose is to

[0048]

Means for Accomplishing the Problems The present invention provides a plastic molded integrated circuit having terminal pins on a package, a plastic molded terminal pin fixing structure for fixing and holding the terminal pins with a predetermined accuracy, and The above object has been achieved by providing an airtight sealing structure for the plastic mold and the terminal pin using a sealing material containing silicon as a component and having adhesiveness and elasticity.

[0049] Furthermore, the present invention achieves the above object by coating the sealing material on the surface of a plastic mold that includes at least a part of the terminal pin fixing structure. .

[0050]

[Operation] In the present invention, in a plastic molded integrated circuit having terminal pins on a package, the terminal pins are fixed with a predetermined precision at or around the interface between the plastic mold and the terminal pins. The terminal pin fixing structure of the holding plastic mold and the airtight sealing structure for the plastic mold and the terminal pin are not the same.

That is, the sealing material for the hermetic sealing structure is as follows:
It does not have to be a component of the plastic molded terminal pin fixing structure, and therefore, the best material can be selected for the properties of this sealing material for use in the hermetically sealed structure.

Therefore, in the present invention, a sealing material containing silicone as a component and having adhesiveness and elasticity is used as the sealing material.

[0053] In the present invention, the sealing material containing silicone is used because it has a lower water absorption rate and higher water repellency than general epoxy resins, and it also has high water repellency, as well as silicone rubber. This is because it is possible to manufacture a sealing material with good adhesion and elasticity.

[0054] According to the sealing material of the present invention, which contains silicon as a component, due to its low water absorption rate, moisture in the air is not absorbed and does not permeate into the inside of the integrated circuit. In addition, in combination with the elasticity of the sealing material, it is possible to reduce the occurrence of cracks due to vaporization of absorbed and condensed moisture due to rapid temperature rise.

Furthermore, since the sealing material of the present invention containing silicone has good water repellency, even if moisture in the air condenses on the surface of the sealing material, gravity will prevent this condensation. The condensed moisture is easily removed and the possibility of this condensed moisture entering the integrated circuit is reduced.

Further, such water repellency can reduce the adhesion of contaminants in the air even if they fall around the terminal pins on the integrated circuit package.

Therefore, in combination with the good adhesion and elasticity of the sealing material of the present invention described above, contaminants that have fallen around the terminal pins on the package are dissolved in the moisture condensed around the terminal pins and accumulated. It is possible to reduce the problem of intrusion into the inside of the circuit.

Furthermore, according to the water repellency of the sealing material of the present invention containing silicon as a component, even if the contaminants that have fallen or adhered to the vicinity of the terminal pins on the package are conductive substances, It is also possible to reduce the possibility that moisture condensing around the terminal pins forms a thin film and lowers the insulation resistance between the plurality of terminal pins.

Therefore, according to the present invention, it is possible to prevent a decrease in insulation resistance due to the adhesion of contaminants such as conductive foreign matter between the terminal pins of an integrated circuit, and to improve the airtightness of the mounting portion of the terminal pins. It is possible to effectively prevent the intrusion of moisture, contaminants, corrosive gas, etc., thereby improving the reliability of the integrated circuit.

[0060]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view of a first embodiment of the present invention. The integrated circuit shown in FIG. 1 is a DIP integrated circuit.

In FIG. 1, the terminal pins 3 of the integrated circuit 1 have a terminal pin fixing structure as indicated by the symbol A, which is fixed and held with a predetermined precision by a plastic mold 12.

[0063] Furthermore, the silicone-containing sealing material 10, which contains silicone as a component and has adhesiveness and elasticity, provides
For some of the plastic molded terminal pins of the above-mentioned terminal pin fixing structure, an airtight sealing structure is constructed as shown by reference numeral B.

According to the first embodiment of the present invention,
Terminal pins 3 of integrated circuit 1 are molded into plastic mold 12.
This allows it to be fixed and held with a predetermined precision.

Furthermore, due to the difference in the coefficient of thermal expansion of the plastic mold 12 and the coefficient of thermal expansion of the terminal pin 3, the plastic mold 12 and the terminal pin 3 may change when the temperature of the integrated circuit changes.
Even if a gap occurs at the interface between the two, the silicone-containing sealing material 10 has elasticity that does not generate stress such as thermal stress, and also has adhesive properties to maintain an airtight sealing structure. is possible.

Furthermore, since the sealing material 10 containing a silicone component is filled around the mounting portion of the terminal pin 3, the water repellency of the silicone contained in this sealing material prevents contaminants floating in the air from falling. However, it becomes difficult to adhere.

Furthermore, even if moisture condenses on the surface of the integrated circuit 1 due to the temperature of the integrated circuit 1 or a rise or fall in air temperature, the condensed moisture will be absorbed by the terminal pins 3 on the surface of the integrated circuit 1. There is no possibility that a thin film will form in the surroundings, and the possibility of lowering the insulation resistance between the terminal pins 3 can also be reduced.

FIG. 2 is a sectional view of the hermetically sealed structure in the first embodiment of the invention described above.

FIG. 2 shows a portion where the surrounding outside air, the surface of the terminal pin 3, and the silicone-containing sealing material 10 are in contact with each other.

[0070] When the temperature of the terminal pin 3 of the integrated circuit and the silicon component-containing sealing material 10 rises or falls,
A change in dimension (thermal expansion) occurs due to the respective predetermined coefficient of thermal expansion. For example, the terminal pin 3 undergoes a dimensional change as shown by arrow L1 due to a decrease or increase in temperature. Further, the silicon component-containing sealing material 10 undergoes a dimensional change as shown by arrow L2 due to a decrease or increase in temperature.

However, due to the elasticity of the silicone-containing sealant 10, these dimensional changes are absorbed, thermal stress is reduced, and the airtight sealing structure between the terminal pin 3 and the silicone-containing sealant 10 is improved. The contact portion B1 can maintain good adhesion and can prevent moisture in the air, contaminants, corrosive gas, and the like from entering into the integrated circuit.

[0072] The adhesion of the sealing material containing silicone as a component of the present invention is preferably improved, but it is determined by at least the amount of dimensional change due to temperature drop or rise and elasticity (elastic modulus). The adhesion force must be greater than the thermal stress applied. For example, even if sufficient adhesion cannot be ensured, by using a sealing material made of a softer material, thermal stress can be reduced and the hermetic seal structure can be prevented from being impaired. can.

FIG. 3 is a sectional view of a second embodiment of the present invention.

The integrated circuit 1 in FIG. 3 is a PGA package integrated circuit.

In FIG. 3, symbols 1, 3, 10, 1
2, A, and B are the same as those with the same symbols in FIG. 1 described above.

Similar to the above-described DIP integrated circuit shown in FIG. 1, the present invention is applied to this PGA package integrated circuit by configuring a terminal pin fixing structure A and an airtight sealing structure B as shown in FIG. Therefore, it is possible to obtain the same effect as in the first embodiment described above.

FIG. 4 is a side view of a third embodiment of the present invention. Moreover, FIG. 5 is a bottom view of this third embodiment.

In FIGS. 4 and 5, the integrated circuit 1
The terminal pin 3 is fixed and held with a predetermined precision by a plastic mold 12, forming a terminal pin fixing structure.

Furthermore, the surfaces of the side and bottom parts of the plastic mold 12 of this integrated circuit 1 are coated with a silicone-containing sealant 10.

Therefore, a good hermetic sealing structure is constructed between the plastic mold 12 and the terminal pin 3 by the sealing material containing silicon as a component and having adhesiveness and elasticity. Similar to the first embodiment,
It is possible to prevent contaminants and corrosive gases from entering the integrated circuit 1 into moisture in the air, and also to reduce a decrease in insulation resistance between the terminal pins 3.

FIG. 6 is a side view of a fourth embodiment of the present invention. Moreover, FIG. 7 is a bottom view of this fourth embodiment.

In FIGS. 6 and 7, the present invention is applied by coating the surfaces of the side and bottom portions of the PGA package integrated circuit with a silicone-containing sealant 10.

[0083] In these FIGS. 6 and 7, symbols 1 and 3
, 10, and 12 are the same as those with the same reference numerals in FIGS. 4 and 5 described above.

As shown in FIGS. 6 and 7, PG
The present invention can also be applied to the A-package integrated circuit 1 by coating it with the silicon component-containing sealant 10, and it is possible to obtain the same effects as in the third embodiment of the present invention described above.

In the third and fourth embodiments of the present invention shown in FIGS. 4 to 7, coating the lower surface of the integrated circuit 1 with the silicone-containing sealant 10 is not necessarily necessary. However, due to the convenience of the coating process, the coating is done all at once. That is, it is only necessary that the terminal pin 3 and the plastic mold 12 around the terminal pin 3 mounting portion be coated.

[0086]

As explained above, according to the present invention, in a plastic molded integrated circuit having terminal pins on a package, it is possible to reduce the adhesion of contaminants such as conductive foreign matter between the terminal pins and the resulting insulation resistance. In addition to preventing a decrease in the terminal pin, the airtightness of the terminal pin mounting area can be improved to prevent or reduce the intrusion of moisture, contaminants, corrosive gas, etc., and the reliability of the integrated circuit can be improved. This excellent effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view of a hermetically sealed structure according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a second embodiment of the invention.

FIG. 4 is a side view of a third embodiment of the invention.

FIG. 5 is a bottom view of the third embodiment.

FIG. 6 is a side view of a fourth embodiment of the present invention.

FIG. 7 is a bottom view of the fourth embodiment.

FIG. 8 is a side view showing contaminant deposition between terminal pins of a DIP integrated circuit.

FIG. 9 is a bottom view showing the adhesion of contaminants between terminal pins of a PGA package integrated circuit.

FIG. 10 is a perspective view showing a gap that occurs at the interface between a plastic mold and a terminal pin of a DIP integrated circuit.

FIG. 11 is a perspective view showing a gap that occurs at the interface between the plastic mold and the terminal pin of a PGA package integrated circuit.

FIG. 12 is a top view showing corrosion and disconnection of aluminum wiring on a wafer chip inside an integrated circuit.

[Explanation of symbols]

1...Integrated circuit, 3...Terminal pin, 5...Wafer chip, 10...Silicone component-containing sealing material, 12...Plastic mold, 30...pad, 32...Aluminum wiring, 34...I/O buffer section, 40...pollutant, A...Terminal pin fixing structure, B...Hermetic sealing structure, C1, C2...Corroded part, D... Gap.

Claims (2)

[Claims] 1. A plastic molded integrated circuit having terminal pins on a package, a plastic molded terminal pin fixing structure for fixing and holding the terminal pins with a predetermined precision, and a silicon molded structure for fixing and holding the terminal pins with a predetermined precision; 1. An integrated circuit characterized by having an airtight sealing structure using a sealing material containing as a component and having adhesiveness and elasticity. 2. According to claim 1, the hermetic sealing structure comprises:
An integrated circuit characterized in that a surface of a plastic mold including at least a portion of the terminal pin fixing structure is coated with the sealing material.